Solve for $x$ and $y$ using substitution. ${4x-y = 1}$ ${x = y+7}$
Explanation: Since $x$ has already been solved for, substitute $y+7$ for $x$ in the first equation. ${4}{(y+7)}{- y = 1}$ Simplify and solve for $y$ $4y+28 - y = 1$ $3y+28 = 1$ $3y+28{-28} = 1{-28}$ $3y = -27$ $\dfrac{3y}{{3}} = \dfrac{-27}{{3}}$ ${y = -9}$ Now that you know ${y = -9}$ , plug it back into $\thinspace {x = y+7}\thinspace$ to find $x$ ${x = }{(-9)}{ + 7}$ ${x = -2}$ You can also plug ${y = -9}$ into $\thinspace {4x-y = 1}\thinspace$ and get the same answer for $x$ : ${4x - }{(-9)}{= 1}$ ${x = -2}$